With respect to an apparatus for allowing a vehicle to move along a preset target course while the movement of the vehicle is automatically induced, it is essential that the apparatus exactly detects the position where the vehicle is presently located, and performances of the apparatus are practically determined depending on how exactly the present position of the vehicle is detected.
A conventional apparatus of the foregoing type which assures that the target course can be changed to another one, i.e., a conventional apparatus of the foregoing type having excellent flexibility in respect of a target course to be assumed by the vehicle is typically disclosed in an official gazette of, e.g., Japanese Laid-Open Patent NO. 70618/1986 which is titled "System for allowing a vehicle to move in an unmanned manner". According to the system of the prior invention, as the vehicle moves, a distance of movement of the vehicle on a two-dimensional coordinate is sequentially calculated with reference to the speed of movement of the vehicle and the orientation angle of movement of the vehicle so that the present position of the vehicle on the two-dimensional coordinate is detected based on the sequentially calculated values.
With the conventional apparatus as described above, the speed of movement of the vehicle is detected by a vehicle speed sensor and the orientation angle of movement of the vehicle is detected by a gyro-compass serving as an orientation sensor. For the reason, it is unavoidable that detection errors derived from these sensors are increased accumulatively. Especially, an error of the running speed appearing due to slippage of tires during movement of the vehicle and an error of the orientation angle appearing due to offset drift of the gyro-compass remarkably degrade the detection accuracy in respect of the position of the vehicle to be detected.
Therefore, the conventional apparatus has a drawback that induction control is generally accomplished with a deteriorated accuracy.
To obviate the foregoing drawback, a proposal has been made such that a station having suitable marks and induction cables laid thereon is installed at a known important location on the target course and a sensor is mounted on the vehicle to detect the magnetic field generated by the marks and the induction cables, whereby the detection error derived from the speed sensor and other components is periodically corrected based on outputs from the sensor. According to the aforementioned proposal having exterior induction units such as marks or the like employed therefor, however, the conventional apparatus has still a drawback that it fails to secure certain flexibility in respect of variation of the target course to another one to be assumed by the vehicle, because the target course is unchangeably determined.
The present invention has been made with the foregoing background in mind.
Therefore, an object of the present invention is to provide an apparatus for controlling the movement of a vehicle wherein the apparatus assures that the movement of the vehicle can exactly be induced while an advantage of flexibility in respect of a target course to be assumed by the vehicle is sustained.